共查询到20条相似文献,搜索用时 15 毫秒
1.
Mohamed Brakta Paul Lhoste Denis Sinou Joseph Banoub 《Journal of mass spectrometry : JMS》1991,26(2):85-88
Electron impact mass spectra at 70 eV electron energy and chemical ionization mass spectra with ammonia as the reagent gas are reported for certain unsaturated C-glycosides. Comparisons are made between the mass spectra of anomeric pairs of these glycosides. 相似文献
2.
Joseph J. Brophy Derek Nelson James S. Shannon Sydney Middleton 《Journal of mass spectrometry : JMS》1979,14(7):379-386
The electron impact and chemical ionization mass spectra of a series of N,N′, -diaryl ureas have been compared. The electron impact mass spectra indicate rearrangements leading to two pairs of aromatic amines and isocyanates, either as ions or molecules. The chemical ionization mass spectra showed the formation of protonated amines and isocyanates via rearrangement. 相似文献
3.
Susan D. Goff Barbara L. Jelus Edward E. Schweizer 《Journal of mass spectrometry : JMS》1977,12(1):33-36
In the 70 e V electron impact mass spectra of a series of alkyldiphenylphosphine oxides (R?2PO, R = Me, Et, n-Pr, i-Pr, n-Bu, i-Bu, t-Bu, neopentyl, n-decyl), molecular ions of low abundance are observed and [M + H]+ ions are formed to a small extent at high sample pressures. The major ions include [?2PO]+, [?2POH]+; [?2CH2PO]+ and [?2CH2POH]+ which are formed by rearrangement and cleavage processes. The chemical ionization mass spectra obtained with methane and isobutane reagents consist of [M + H]+ ions. The proton affinity of R?2PO was found to be 219 ± 2.5 kcal mol?1. 相似文献
4.
P. S. Kulkarni H. V. Kamath Sheshgiri N. Kulkarni 《Journal of mass spectrometry : JMS》1984,19(7):334-342
The electron impact and methane and ammonia chemical ionization mass spectra of some selected nitro-substituted isomeric benzalacetophenones, benzyl ketones and aromatic epoxides have been examined. The isomeric pairs show significant differences in the electron impact and chemical ionization spectra. The EI spectra show cleavage α to the carbonyl as the major fragmentation mode. Under CI conditions subtle differences in the fragmentation modes of isomeric pairs are more enhanced, and elimination reactions are more favoured in the o-nitro-substituted compounds than in the para isomers. 相似文献
5.
The electron impact and chemical ionization mass spectra of a number of aliphatic and aromatic glycidyl ethers are reported. For electron impact spectra, partial fragmentation pathways have been determined by metastable linked scan techniques. 相似文献
6.
J. A. Rowley 《Journal of mass spectrometry : JMS》1989,24(11):997-1000
The positive electron impact (EI) and isobutane chemical ionization (CI) mass spectra of six nitramine nitrates were studied with the aid of some accurate mass measurements. In the EI spectra, β fission relative to both the nitramine and nitrate ester is important. In the CI spectra a major ion occurs at [MH – 45]+ and was found to be mainly due to [M + 2H ? NO2]+. All of the compounds except N-(2 hydroxyethyl)-N-(2′,4′,6′-trinitrophenyl)nitramine nitrate gave an [MH]+ ion. The [MH – 45]+ ion in the isobutane CI mass spectra of tetryl is also due to [M + 2H ? NO2]+. 相似文献
7.
William J.A. Vandenheuvel Robert W. Walker Steven B. Nagelberg Bennett R. Willeford 《Journal of organometallic chemistry》1980,190(1):73-82
The mass spectrometric behavior of a) the tricarbonylchromium complexes of a series of aromatic hydrocarbons, b) the dimethyldiphenyl compounds of the Group IV elements (i.e., diphenylpropane, dimethyldiphenylsilane, etc.) and c) the mono- and bis-tricarbonylchromium complexes of these ligands under electron impact and chemical ionization conditions are reported. The MH+ ion is base peak for all of the simple arenetricarbonylchromium complexes using chemical ionization, whereas [M — 3 CO]+ or 52Cr+ dominate the spectra with electron impact ionization. The chemical ionization spectra of the series of Group IV element ligands do not exhibit signals in the molecular ion region, the base peak being [M — Ph]+. [M — CH3]+ is the electron impact base peak for each of the ligands except the lead-containing compound, for which the base peak is 208Pb+. The mono-tricarbonylchromium complexes yield chemical ionization molecular ion clusters, but their base peaks arise via fragmentation of the Group IV element—aromatic ring bonds. Electron impact ionization spectra of the mono complexes are characterized by losses of CO and the production of Cr+ ions, neither of which occurs with chemical ionization. For the series of bis-tricarbonylchromium complexes, an MH+ ion is prominent only in the chemical ionization spectrum of the diphenylpropane complex. The electron impact induced spectra of the bis-tricarbonylchromium complexes are similar to those of the mono-complexes in that loss of CO is a prominent feature. 相似文献
8.
Janusz Moskal Krzysztof Nagraba Aleksandra Moskal 《Journal of mass spectrometry : JMS》1976,11(9):955-963
The mass spectra of α,β-diarylaminocrotonic acid anilides have been determined and the fragmentation pathways are now discussed. The proposed pathways have been confirmed by deuterium labelling, the spectrum of the model compound, or the appropriate metastables. The detailed electron impact data are given. 相似文献
9.
D. V. Bowen P. W. Skett J. Thorpe A. O. Plunkett 《Journal of mass spectrometry : JMS》1984,19(6):285-290
Electron ionization (EI) spectra and both positive and negative chemical ionization (CI) spectra have been obtained for four isoquinolinium ylides and two pyridinium ylides. Electron transfer reactions dominate the CI mass specra. The base peak in negative chemical ionization is the [M]?· ion, formed by electron capture. In the positive methane CI spectra the molecular ion, [M]+·, is relatively more intense than [MH]+ showing electron transfer to be the main positive ionization process. In the positive ammonia CI spectra, proton transfer to give [MH]+ is the main ionization process, but electron transfer is also observed. The EI spectra show fragmentations in which the aromatic nitrogen moiety retains the charge and fragmentation is by loss of radicals or small neutral molecules from the side-chains. Radical driven reactions are proposed to explain these spectra. 相似文献
10.
Pirjo Vainiotalo Pentti J. Mlknen Anto Vainiotalo 《Journal of mass spectrometry : JMS》1989,24(6):415-420
The electron impact induced fragmentations of 24 tetrahydropyrane ethers of different types of alcohols were studied by exact mass measurement and metastable ion analysis. The most characteristic features of the spectra were associated with the tetrahydropyrane ring, As the size of the molecule increased, the fragmentations with respect to exocyclic oxygen became more important allowing differentiation among the isomeric aliphatic alcohols. Under isobutane chemical ionization, loss of neutral alcohol from [M + H]+ leading to the formation of a tetrahydropyranium ion was dominant for aliphatic alcohol derivatives, whereas loss of 2-hydroxy tetrahydropyrane giving rise to an alkyl ion was dominant for bicyclic alcohol derivatives. Under ammonia chemical ionization, nucleophilic substitution reactions were always most important. 相似文献
11.
E. Constantin F. H. Kotzyba-Hibert J. M. Lehn P. Traldi 《Journal of mass spectrometry : JMS》1987,22(1):13-16
Mass spectra of some macropolycycles have been studied. Normal and metastable (B/E) mass spectra are presented. The fragmentation patterns and the structures of the main ions are discussed. 相似文献
12.
13.
Phosphate esters are important commercial products that have been used both as flame retardants and as plasticizers. To analyze these compounds by gas chromatographic mass spectrometry, it is important to understand the mass spectra of these compounds using various ionization modes. This paper is a systematic overview of the electron impact (EI), electron capture negative ionization (ECNI) and positive chemical ionization (PCI) mass spectra of 13 organophosphate esters. These data are useful for developing and optimizing analytical measurements. The EI spectra of these 13 compounds are dominated by ions such as H4PO4+, (M ? Cl)+, (M ? CH2Cl)+ or (M)+ depending on specific chemical structures. The ECNI spectra are generally dominated by (M ? R)?. The PCI spectra are mainly dominated by the protonated molecular ion (M + H)+. The branching of the alkyl substituents, the halogenation of the substituents and, for aromatic phosphate esters, ortho alkylation of the ring are all significant factors controlling the details of the fragmentation processes. EI provides the best sensitivity for the quantitative measurement of these compounds, but PCI and ECNI both have considerable qualitative selectivity. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
14.
Summary The mass spectra obtained by electron impact ionization (EI) of dimethyltrisulfide, both at constant sample pressure and during elution from a GC column, are essentially identical, with the molecular ion Me2S
3
+
providing the basis peak. Masses heavier than the molecular ion are not observed. Chemical ionization, using nitrogen, methane or isobutane, gives rise to numerous ions of larger mass than that of the molecular ion. Particularly characteristic are sulfonium type structures Me3S
n
+
, with n=3–6. In addition, radical cations of the type Me3SnCH
2
+
and protonated trisulfide, Me2S3H+, are observed, even with N2 as ionizing gas, together with a variety of ions of lower hydrogen content. Further, a large number of ion types of lower mass than the parent molecule are formed. The mass distribution of ions in the spectrum is found to be highly dependent on the partial pressure of dimethyltrisulfide in the ion source. These phenomena were investigated and accounted for semiquantitatively.
Die EIund CI-Massenspektren des Dimethyltrisulfids
Zusammenfassung Dimethyltrisulfid liefert nach Elektronenstoßionisation bei konstantem Probendruck und bei GC-Probeneinlaß im wesentlichen identische Massenspektren. Das Molekülion Me2S 3 + stellt dabei den Basispeak dar. Größere Massen als die des Molekülions wurden nicht beobachtet. Bei chemischer Ionisation unter Verwendung von Stickstoff, Methan oder Isobutan als Reaktantgas entstehen zahlreiche Ionen mit höherer Masse als der des Molekülions. Charakteristisch sind hierbei sulfoniumartige Strukturen Me3S n + mit n=3–6. Daneben beobachtet man Radikalkationen des Typs Me2SnCH 2 + und protoniertes Trisulfid Me2S3H+ auch bei Ionisation mittels N2 sowie Ionenarten mit einem geringeren Wasserstoffgehalt. Weiterhin wird eine größere Anzahl von Ionenarten gebildet, deren Massen kleiner sind als die des Stammoleküls. Die Massenverteilung der Ionen im Spektrum hängt außerordentlich stark vom Partialdruck des Dimethyltrisulfids in der CI-Quelle ab. Diese Abhängigkeiten wurden semiquantitativ untersucht und dargestellt.相似文献
15.
本文报道苦玄参苷类(picfeltarraenins)(1~5)、膜荚黄芪苷类(astramembrannins)(6~8)、雪胆素苷类(hemsamabilinins)(9,10)及其O-乙酰衍生物(11,12)和洋地黄毒苷(digitoxin)(13)的负离子化学电离质谱.用甲烷和二氯甲烷作为混合反应气,获得了满意的结果.谱中有特征的M~(?)或[M-1]~-,[M+Cl]~-和一系列脱糖基的碎片离子[M+Cl-nR]~-(R为不同类型的糖基)及糖基碎片离子[R+Cl]~-.乙酰化的糖苷还给出[M+Cl-nCH_2CO]~-或[M+Cl-nCH_3COOH]~-等碎片离子. 相似文献
16.
17.
Antigoni Kotali 《Journal of mass spectrometry : JMS》1991,26(10):889-891
The electron impact mass spectra of the new synthesized dioximes of o-diacyl benzenes (2) are reported. In addition to the molecular ion, characteristic peaks appear at values corresponding to the [M ? OH] +, [M ? NOH]+ and [M ? NHOH]+ ions. No initial dehydration of the molecular ion has been observed. 相似文献
18.
Leopoldo Ceraulo Mirella Ferrugia Vincenzo Sprio 《Journal of mass spectrometry : JMS》1992,27(1):37-38
The positive-ion electron impact ionization mass spectra of eight substituted 3-nitropyrroles were examined. The major fragment ions arise by ortho interactions between the 3-nitro group and the 2-methyl or 2-aryl group. 相似文献
19.
The electron impact and methane chemical ionization mass Spectrometry of fifteen trisilanes and trisiloxanes containing various substituents was studied with the aid of exact mass measurements and metastable ion analyses. Migration reactions of the two kinds of compounds are discussed. 相似文献
20.
Esa Mki Kalevi Pihlaja Imre Huber Ferenc Fülp Gbor Bernth Pirjo Vainiotalo 《Journal of mass spectrometry : JMS》1993,28(1):18-22
The electron impact ionization mass spectra of dipyrido [1,2-a:4,3-d]pyrimidinones are strongly influenced by the degree of aromaticity of the fused rings. The molecular ions of the compounds are fairly stable. The main routes of fragmentation involve formation of the [M – H]+ ion and loss of substituents, H2CN˙, CO and alkyl radicals. 相似文献